1. Field of the Invention
The invention relates to a ceramic lamp having a lamp vessel made of translucent ceramic and using a hermetically sealing body of electrically conductive cermet to route current into the lamp vessel, the sealing body being hermetically sealed relative to sealing portions of the lamp vessel via a sealing material.
2. Description of Related Art
In a ceramic lamp, in which the lamp vessel is made of a translucent ceramic and an electrically conductive cermet is used for the hermetically sealing body, and thus current is routed into the lamp vessel, and in which the lamp vessel is hermetically sealed relative to the sealing body using a sealing material, conventionally several sealing processes are performed.
FIG. 11 shows, for example, an arrangement in which a hermetically sealing tube portion 3 is connected on opposite ends of a bulb portion 2, and the periphery of a hermetically sealing bodies 4 of electrically conductive cermet are sealed relative to the inside wall of the tube portions 3 of the lamp vessel 1 using a sealing material 5, and thus, hermetically sealed portions 7 are formed. One such lamp is described, for example, in laid-open Japanese Patent Application HEI 8-264155.
Furthermore, a process is known in which, in one of the hermetically sealed ends of a lamp with bilateral hermetic seals (of the double-end type), a hermetically sealing body of electrically conductive cermet and a hermetically sealed tube portion of the lamp vessel are sintered to one another in one part, and in which the other hermetically sealed end, upon evacuation of the lamp, is sealed with a sealing material.
Moreover, a process is known in which thin molybdenum tubes are pushed through the hermetically sealing bodies of electrically conductive cermet, embedded and sintered in part with the lamp vessel, and in which evacuation is performed through the molybdenum tube.
However, if the hermetically sealing bodies of electrically conductive cermet are enclosed with a sealing material in a hermetically sealed tube, there are differences in the coefficients of linear expansion between the respective components of the hermetically sealed portions, i.e., between the hermetically sealed tube, the hermetically sealing body, the sealing material and the electrically conductive supply component, such as the upholding part of the electrode and the like. Therefore, there are cases in which cracks form in these hermetically sealing portions, or as a result of these cracks, leaks occur. In the hermetically sealed portions of a conventional ceramic lamp in which the electrically conductive cermet which is conventionally present is used as the hermetically sealing body, to date sufficiently reliability could not be achieved.